Abstract:Ultrastructure of the spermatozoon of Sepia esculenta Hoyle was observed by scanning and transmission electron microscopy. The sperm is 191.84μm (n=10) long and consists of two parts, the head and the tail. The head is mainly composed of acrosome and nucleus, and the tail includes the middle piece, the principal piece, and the end piece. The acrosome was an inverted U-shaped cystid, and the subacrosomal space was ∩-shaped. The nucleus was long, slightly curved and cylindrical-shaped, and was filled with homogeneous texture with high electron density. The posterior nuclear fossa diverged from the center of the nucleus. The middle piece of the tail is very long and consists of mitochondria spur and flagellum incompletely encircled. The mitochondria spur includes two parts, the proximal part and the distal part. The proximal part contained a great amount of mitochondria, while the distal part contained no mitochondria. The principal piece of flagellum is slender, and is composed of a “9+2”axoneme surrounded by nine bundles of coarse fibers, and it formed the typical structure of “9+9+2”
